1. Field of the Invention
This invention relates to a sensor for sensing the delay difference or relative phase between two signals of like wave form and more particularly to such device employing surface acoustic waves.
2. Description of the Prior Art
Production of surface acoustic waves in crystalline substrates of lithium niobate and the like and the utilization of such waves has been employed to produce numerous useful devices. Among such devices are filters (U.S. Pat. No. 3,663,899), optical domain shifting devices (U.S. Pat. No. 3,701,122), correlators and convolvers (U.S. Pat. Nos. 3,770,949; 4,037,174; and 4,099,146), delay devices (U.S. Pat. Nos. 3,918,012 and 3,840,826) and transformers between the time and frequency domain (U.S. Pat. Nos. 3,803,395 and 3,925,653).
U.S. Pat. No. 4,016,513 discloses a convolver having two interdigital acoustoelectric transducers disposed on a crystalline surface in spaced apart relation. Between the two input transducers is an output transducer which is oriented obliquely of the input transducers. The signal produced at the output transducer is the convolution of the signals applied to the input transducer.
U.S. Pat. No. 4,024,480 discloses a filter having two closely spaced input transducers formed on a crystalline surface and a plurality of staggered output transducers disposed on a remote portion of the surface. The individual output transducers, which are oriented in an oblique or staggered position, constitute taps on a delay line, the amount of delay occurring at a given output transducer being a function of its physical location with respect to the input transducers.
U.S. Pat. No. 4,114,116 discloses a surface acoustic wave signal processor having two obliquely oriented input transducer arrays and a plurality of output transducers formed on a line normal to the surface acoustic waves produced by the input transducer arrays. Each individual transducer in the input arrays is spaced from the transducers adjacent to it by a multiple of the wave length of the acoustic wave so as to produce at each individual output transducer a unique combination of the signals applied to the two input transducers.